Acrylic plate with heat-sensitive and temperature-sensitive properties and preparation method thereof

Abstract

The invention discloses an acrylic plate with temperature-sensitive heat-sensitive performance and a preparation method thereof, and relates to the technical field of compositions of temperature-sensitive heat-sensitive high-molecular compounds. The acrylic plate is prepared from the following raw materials in parts by mass: 60-90 parts of matrix resin, 5-30 parts of a thermosensitive color-changing material, 0.5-5 parts of a light stabilizer, 3-15 parts of a toughening agent and 0.1-2 parts of a processing aid. Through the synergistic effect of the specific light stabilizer, the flexibilizer and the processing aid, the inherent high transparency of the acrylic plate is effectively maintained, the good mechanical property of the material is ensured, and the defects of transparency reduction, brittleness increase and the like which are often caused by addition of a heat-sensitive material are overcome. The selected light stabilizer with a special structure remarkably improves the ultraviolet degradation resistance of the material, and effectively prevents yellowing, embrittlement and discoloration performance degradation of the material in long-term use or outdoor environment, thereby prolonging the service life of the product and improving the reliability of the product.

Description

Technical Field

[0001] The present invention relates to the technical field of thermosensitive polymer compound compositions, and in particular to an acrylic plate with thermosensitive properties and a preparation method thereof. Background Art

[0002] In today's society, with the continuous advancement of science and technology and the improvement of people's living standards, the demand for materials with special properties is also growing. Acrylic sheet, as a widely used polymer material, is widely used in advertising signs, lighting fixtures, display windows and other fields due to its excellent transparency, mechanical properties, and easy processing. However, traditional acrylic sheet focuses mainly on basic physical properties and appearance, with relatively simple functions. When faced with some special needs, such as temperature indication, smart packaging, and building energy conservation, traditional acrylic sheet seems to be unable to meet the needs.

[0003] At the same time, the research and application of thermosensitive materials has gradually gained momentum. These materials can undergo a reversible color change in response to temperature fluctuations, providing a visual indication of temperature and bringing new possibilities and solutions to numerous fields. However, successfully imparting thermosensitive properties to acrylic sheets is not a simple task. On the one hand, it is necessary to address the compatibility issues between the thermosensitive material and the acrylic matrix resin to ensure uniform dispersion and stable performance. On the other hand, it is also necessary to ensure the sensitivity and accuracy of the thermal response, while maintaining the excellent performance of the acrylic sheet, so that it can meet the temperature monitoring and indication requirements of practical applications.

[0004] Existing technologies attempt to add thermochromic materials to acrylic sheets to achieve temperature-sensitive and thermosensitive properties, but these often face numerous challenges in practice. For example, the added thermochromic materials can lead to reduced transparency and mechanical properties, hindering their proper use and widespread adoption. Furthermore, key performance indicators such as the temperature range, speed, and durability of the thermochromic materials are difficult to achieve, limiting their widespread adoption in practical applications. Therefore, developing an acrylic sheet with excellent temperature-sensitive and thermosensitive properties and stable overall performance has become a pressing technical challenge. Summary of the Invention

[0005] This invention aims to address the problems of existing acrylic sheets, which suffer from limited functionality, poor transparency and mechanical properties, and inadequate thermal response. Through a carefully designed formulation and process, this invention provides an acrylic sheet with excellent thermal sensitivity. This sheet not only exhibits a sensitive thermal response, but also exhibits excellent stability, a precise color change range, and strong durability, while maintaining excellent transparency and mechanical properties. It is suitable for applications requiring specialized temperature monitoring, such as temperature indicators, smart packaging, and energy-saving windows in buildings.

[0006] To achieve the above object, the technical solution adopted by the present invention is: an acrylic sheet with temperature-sensitive and thermosensitive properties is made of the following raw materials in parts by weight: 60-90 parts of base resin, 5-30 parts of thermochromic material, 0.5-5 parts of light stabilizer, 3-15 parts of toughening agent, and 0.1-2 parts of processing aid; The light stabilizer has a structure shown in Formula 1: Formula 1; The Z1 is selected from the group consisting of: O, S, N(H), and C(CH3)2.

[0007] Furthermore, the matrix resin is selected from: polymethyl methacrylate.

[0008] Furthermore, the thermochromic material is selected from a metal oxide system in which cobalt oxide and aluminum oxide are compounded in a mass ratio of 1:(3-5).

[0009] Furthermore, the light stabilizer is selected from any one of the compounds shown in the following structures: ; ; ; .

[0010] Furthermore, the toughening agent is selected from: dibutyl phthalate.

[0011] Furthermore, the processing aid is selected from: zinc stearate.

[0012] A method for preparing an acrylic sheet having temperature-sensitive and heat-sensitive properties comprises the following steps: S1 premix: The base resin, thermochromic material, light stabilizer, toughening agent and processing aid are added to a high-speed mixer and mixed for 10-30 minutes to obtain a premix; S2 melt extrusion: The premix was fed into a twin-screw extruder, controlling the temperature of a zone at 160°C-170°C, a zone at 170°C-180°C, a zone at 175°C-185°C, a screw speed of 50-150rpm, and a melt; S3. Compression molding: The melt is pressed into shape by a flat vulcanizer at a pressure of 5-15 MPa for 5-15 minutes, cooled to below 40°C and demolded to obtain a method for preparing an acrylic sheet having temperature-sensitive and thermosensitive properties.

[0013] Furthermore, the die head temperature of the twin-screw extruder in S2 is controlled at 170° C.-180° C., and the vacuum degree is ≥0.08 MPa.

[0014] Furthermore, the cooling in S3 is air cooling.

[0015] The invention discloses an acrylic sheet with temperature-sensitive properties and its application in temperature indicators, smart packaging or energy-saving windows of buildings.

[0016] The mechanism of action of the light stabilizer (hindered amine light stabilizer, HALS) described in the present invention in the thermosensitive acrylic sheet is primarily based on its efficient free radical capture ability. When the material is exposed to ultraviolet (UV) light, the UV energy triggers a photooxidation reaction in the acrylic sheet's matrix resin, generating highly active alkyl radicals. The key active group in the light stabilizer molecule described in the present invention is the tertiary amine group, which rapidly captures these initially generated alkyl radicals to form relatively stable hindered amine nitroxide radicals, thereby preventing the initiation of the free radical chain reaction. The light stabilizer described in the present invention protects the matrix resin (PMMA) from UV-induced photooxidative degradation during processing and use, especially in outdoor or illuminated environments. This degradation can lead to yellowing, embrittlement, surface cracking, decreased transparency, and loss of mechanical properties (strength and toughness). The light stabilizer effectively inhibits this process through the aforementioned mechanism, maintaining the sheet's transparency, strength, and long-term stability. Inorganic thermochromic materials such as cobalt oxide / aluminum oxide are usually relatively stable to light (especially ultraviolet light), but the stability of their dispersion system and matrix resin is crucial to their functionality. Light stabilizers protect the PMMA matrix from photodegradation, indirectly stabilize the environment in which the thermochromic material is located, and prevent uneven dispersion, agglomeration or degradation of the color-changing performance of the thermochromic material caused by matrix degradation. At the same time, light stabilizers may also directly inhibit the negative impact that light may have on certain color-changing materials. By preventing photooxidative degradation, light stabilizers ensure that acrylic sheets with added thermochromic materials and other additives maintain their key properties such as temperature-sensitive and thermosensitive properties, mechanical strength, toughness, surface gloss and transparency during long-term use, especially in application scenarios that require exposure to light (such as building energy-saving windows, outdoor signs), thereby extending the service life of the material. Light stabilizers are one of the key additives for improving the weather resistance (resistance to ultraviolet light and resistance to thermal oxidative aging) of polymer materials. In the present invention, it significantly improves the outdoor applicability of temperature-sensitive and thermochromic acrylic sheets.

[0017] The matrix resin described in this invention provides the acrylic sheet with its fundamental transparency, rigidity, surface gloss, and ease of processing. A high proportion (60-90 parts) ensures the sheet's core performance. Its excellent optical clarity provides a visible window for the thermochromic effect. Its excellent melt flowability (compatible with subsequent processing) ensures uniform dispersion of the other components.

[0018] The thermosensitive color-changing material described in the present invention gives the material thermosensitive properties. Cobalt oxide is the main color-changing substance, and aluminum oxide serves as a carrier and diluent. Too much aluminum oxide will reduce the color change sensitivity, while too little may cause the color change temperature to be too high or unstable. This ratio optimizes the color change temperature range and color contrast. The transparency of PMMA makes the color change process clearly visible. The addition of toughening agents prevents the increase in brittleness caused by the addition of large amounts of inorganic powders. Light stabilizers protect PMMA and the color change system from ultraviolet light degradation, maintaining the long-term stability and accuracy of the color change performance. Processing aids improve the dispersion and lubrication of powders in molten PMMA, prevent agglomeration, and ensure color change uniformity and response sensitivity.

[0019] The toughening agent described in the present invention improves toughness and prevents brittle cracking. The addition of a heat-sensitive color-changing material (cobalt oxide / aluminum powder) significantly increases the brittleness of PMMA. The toughening agent dibutyl phthalate (DBP) acts as a small molecule plasticizer, infiltrating between PMMA molecular chains, increasing segment mobility, and effectively improving impact strength and toughness. It improves melt flowability and processing window, which is conducive to subsequent extrusion and compression molding. The dosage range of 3-15 parts, while ensuring the toughening effect, avoids excessive amounts that cause the material to be too soft, the heat distortion temperature to drop significantly, or the DBP migration and precipitation problem.

[0020] The processing aid described in the present invention improves processing fluidity and dispersibility and assists in demolding. As a lubricant and dispersant, zinc stearate reduces internal friction between particles and adhesion to the metal surface of the equipment, ensuring that the powder is highly evenly dispersed in the matrix. This is crucial for the uniformity and response sensitivity of thermosensitive color change. It reduces melt viscosity, making it easier to transport, mix and plasticize the material in the twin-screw extruder, ensuring process stability. In the compression molding (S3) stage, it acts as an internal lubricant, facilitating the melt to escape from the mold and obtain a sheet with a smooth surface.

[0021] The present invention closely combines formula design (component selection and proportion) with optimized process parameters (mixing, extrusion, and pressing), allowing each component to exert its own function and promote each other, ultimately synergistically solving many problems existing in traditional technologies and successfully preparing functional acrylic sheets with high transparency, good mechanical properties, sensitive and stable thermal color-changing effects, and excellent weather resistance.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. Significantly improved thermochromic performance: By optimizing the ratio of thermochromic materials (cobalt oxide / aluminum oxide composite system) and the compatibility design with the matrix resin, the response sensitivity of the acrylic sheet to temperature changes is significantly improved, and the stability and accuracy of the color change process are enhanced, solving the problems of insensitive color change, inaccurate range or easy inactivation in traditional methods.

[0023] 2. Basic performance is well maintained: Through the synergistic effect of specific light stabilizers (Formula 1 structure), toughening agents (such as DBP) and processing aids (such as zinc stearate), the inherent high transparency of acrylic sheets is effectively maintained, and the material is ensured to have good mechanical properties (such as tensile strength and impact strength), overcoming the defects of decreased transparency and increased brittleness often caused by the addition of heat-sensitive materials.

[0024] 3. Significantly enhanced weather resistance and service life: The special structural light stabilizer selected significantly improves the material's ability to resist UV degradation (weather resistance), effectively preventing the material from yellowing, brittleness, and discoloration performance degradation under long-term use or outdoor conditions, thereby extending the product's service life and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The light stabilizer 1 of the present invention 1 HNMR spectrum. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] Synthesis example 1 Synthesis of Light Stabilizer 1: ; The first step: Under a nitrogen atmosphere, 20 g of raw material 1, 16.72 g of raw material 2, 16.89 g of anhydrous potassium carbonate, 2.12 g of tetrakis(triphenylphosphine)palladium and 200 g of a mixed solution of toluene, ethanol and water in a volume ratio of 2:1:1 were added to the reaction system, heated to 95 ° C and refluxed for 10 hours, turned off the heating, cooled to room temperature, allowed to stand and separated, the aqueous phase was extracted twice with ethyl acetate, the organic phases were combined, the organic phases were dried over anhydrous magnesium sulfate, filtered, and dried, and silica gel column chromatography was performed using a mixture of petroleum ether and ethyl acetate as eluent, and dried to obtain 20.50 g of intermediate 1.

[0028] Step 2: Under nitrogen protection, 20.50g of intermediate 1, 23.45g of raw material 3, 25.36g of potassium phosphate trihydrate, 0.06g of pyridine-2-carboxylic acid, 0.45g of CuI and 250g of DMSO were added to the reaction system in sequence, and heated at 85°C for 16h; after cooling, the reaction mixture was extracted with aqueous ammonia solution and methyl tert-butyl ether, and the organic phase was washed five times with water and then twice with saturated NaCl solution; finally, the combined organic phase was dried over anhydrous magnesium sulfate, filtered, spin-dried, and subjected to silica gel column chromatography using a mixture of petroleum ether and ethyl acetate as eluent to obtain 29.00g of light stabilizer 1. Structural identification: M / Z [MS+1] of intermediate 1: 431; M / Z[MS+1] of photostabilizer 1: 760; Light stabilizer 1 1 HNMR Chloroform-d: δ8.28-8.21(m,1H),8.11(d,1H),7.99(m,1H),7.89(d,1H),7 .79(dd,1H),7.52(dd,1H),7.37(dd,1H),7.31-7.22(m,1H),6.86(d,1H),6.3 3(d,1H),5.87-5.72(m,2H),4.47(p,1H),4.02(m,1H),3.24(d,3H),2.41(dd, 6H),2.01(m,4H),1.76(m,4H),1.62(s,2H),1.32-1.11(m,21H),1.07(s,3H).

[0029] Synthesis Example 2-Synthesis Example 4 Light Stabilizers 2 to 4 were synthesized by following the same preparation method as in Synthesis Example 1, except that Raw Material 2 was substituted. The structures of Raw Material 2, Light Stabilizers 2 to 4, and their M / Z [MS+1] values ​​are shown in Table 1.

[0030] Table 1. Structures of raw material 2, light stabilizers 2-4, and M / Z [MS+1] data involved in synthesis examples 2-4.

[0031]

[0032] Example 1 Preparation of an acrylic sheet with temperature-sensitive properties: 1. Raw material ratio: Matrix resin: polymethyl methacrylate (PMMA, molecular weight approximately 100,000 g / mol), 80 parts; Thermochromic material: cobalt oxide (CoO, purity ≥99%, particle size ≤5μm) and aluminum oxide (Al2O3, purity ≥99.5%, particle size ≤10μm) are compounded in a mass ratio of 1:4, with a total dosage of 10 parts; Light stabilizer: 2 parts of light stabilizer 1 obtained in Synthesis Example 1; Toughening agent: dibutyl phthalate (DBP, purity ≥99%), dosage 5 parts; Processing aid: zinc stearate (purity ≥98%, particle size ≤50μm), dosage 0.5 parts.

[0033] 2. Preparation method: S1. Premix: 80 parts of polymethyl methacrylate, 2 parts of cobalt oxide, 8 parts of aluminum oxide, 2 parts of light stabilizer 1, 5 parts of dibutyl phthalate and 0.5 parts of zinc stearate were added to a high-speed mixer (mixing parameters: speed 800 rpm, mixing time 20 minutes) until the materials were evenly dispersed to obtain a premix.

[0034] S2. Melt Extrusion: The premix was fed into a twin-screw extruder. Extrusion parameters were controlled as follows: temperature zones: zone 1 165°C, zone 2 175°C, zone 3 180°C; screw speed: 100 rpm; die temperature: 175°C; vacuum: 0.09 MPa. Extrusion continued for 10 minutes to obtain a uniform melt.

[0035] S3. Pressing: Transfer the melt to a flatbed vulcanizer. Pressing parameters: Pressure: 10 MPa, Dwell time: 10 minutes, Cooling method: Air cooling, cooling rate controlled at 5°C / min. Demolding is performed after the sheet temperature drops to 35°C, resulting in a 5mm thick acrylic sheet with temperature-sensitive properties.

[0036] Example 2-Example 4 An acrylic plate with temperature-sensitive and thermosensitive properties was prepared by referring to the preparation method of Example 1, except that the light stabilizer therein was replaced with light stabilizer 2 to light stabilizer 4 synthesized in Synthesis Examples 2 to 4, and the rest remained the same as Example 1.

[0037] Comparative Example 1 An acrylic plate with temperature-sensitive and heat-sensitive properties was prepared by referring to the preparation method of Example 1, except that the light stabilizer was replaced by comparative compound 1, and the rest remained the same as Example 1.

[0038] Comparative compound 1: .

[0039] Comparative Example 2 An acrylic plate with temperature-sensitive and heat-sensitive properties was prepared by referring to the preparation method of Example 1, except that the light stabilizer was not added, and the rest of the steps were the same as those of Example 1.

[0040] Comparative Example 3 An acrylic plate with temperature-sensitive and heat-sensitive properties was prepared by referring to the preparation method of Example 1, except that the mass fraction of the toughening agent was changed to 0.5 parts, and the rest remained the same as in Example 1.

[0041] Comparative Example 4 An acrylic plate with temperature-sensitive and heat-sensitive properties was prepared by referring to the preparation method of Example 1, except that the mass fraction of the processing aid was changed to 8 parts, and the rest remained the same as Example 1.

[0042] Comparative Example 5 An acrylic sheet with temperature-sensitive and heat-sensitive properties was prepared by referring to the preparation method of Example 1, except that the light stabilizer was replaced with light stabilizer 770 (CAS: 52829-07-9). The remaining steps were the same as in Example 1. Light stabilizer 770 is a commonly used light stabilizer in industry.

[0043] Performance testing: 1. Appearance: The appearance of the acrylic sheets with temperature-sensitive and heat-sensitive properties prepared in the examples and comparative examples was evaluated. The data is shown in Table 2.

[0044] 2. Tensile Strength and Impact Strength Determination: The tensile strength and impact strength of the acrylic sheets with temperature-sensitive properties prepared in the examples and comparative examples were tested in accordance with GB / T 7134-2008. The data are shown in Table 2.

[0045] Table 2. Performance test of an acrylic plate with temperature-sensitive and heat-sensitive properties prepared in the examples and comparative examples.

[0046]

[0047] All examples maintained a "transparent and uniform" appearance. This demonstrates that, with the optimized formulation, the material possesses excellent optical properties and uniformity, with no noticeable defects or discoloration. This consistency reflects the effectiveness of the light stabilizer in UV protection, as well as the contributions of the toughening agent and processing aid to dispersion and uniformity. Comparative Examples 1 and 5 exhibited "slight turbidity," indicating that improper light stabilizer selection can lead to a slight decrease in transparency, but the impact is relatively limited. Comparative Example 2 exhibited a "transparent but slightly yellowish" appearance, indicating that the absence of a light stabilizer can cause a slight yellowing of the material, likely due to degradation of the matrix resin by UV light. Comparative Example 3 exhibited a "transparent but brittle" appearance, indicating that insufficient toughening agent results in a material that remains transparent but has a brittle internal structure, susceptible to cracking or breaking. Comparative Example 4 exhibited a "turbid and speckled" appearance, reflecting that an excess of processing aid can lead to uneven dispersion, resulting in defects or speckling, severely degrading the appearance. Light stabilizers are crucial for maintaining transparency and color stability; insufficient toughening agent can cause brittleness but does not directly affect transparency; excessive processing aid can cause dispersion issues and significantly reduce uniformity.

[0048] The tensile strength of all embodiments is at a high level and has a small range of variation. This shows that under the optimized formula, the material has excellent tensile resistance and good mechanical stability. This trend is due to the integrity of the matrix resin (PMMA), the uniform dispersion of the thermochromic material, and the protective effect of the light stabilizer on the resin. The tensile strength of the comparative examples generally decreases, but the degree of decrease varies due to formulation defects: the tensile strength of comparative examples 1 and 5 is slightly lower than that of the embodiment, indicating that improper light stabilizers will slightly weaken the rigidity of the material, but the effect is relatively mild. The tensile strength of comparative example 2 is significantly reduced, reflecting that the lack of light stabilizers will cause photodegradation of the material, thereby reducing the mechanical strength. The tensile strength of comparative example 3 decreases significantly, indicating that insufficient toughening agent will make the material brittle and the tensile resistance will be sharply weakened. The tensile strength of comparative example 4 is also relatively low, indicating that excessive processing aids can cause internal defects and weaken the overall structure of the material.

[0049] The impact strength of all examples is high and remains stable. This shows that under the optimized formula, the material has good toughness and impact resistance, and can effectively resist external impact or fracture. The appropriate addition of toughening agent is key, which improves the flexibility of the matrix resin, and the light stabilizer protects the material from environmental stress. The impact strength of the comparative examples is generally reduced, and the difference in the degree of decline is significant: the impact strength of comparative examples 1 and 5 is slightly lower than that of the embodiment, indicating that improper light stabilizers will slightly reduce toughness, but not as serious as other comparative examples. The impact strength of comparative example 2 is relatively low, reflecting that the lack of light stabilizer makes the material more brittle and the impact resistance is weakened. The impact strength of comparative example 3 drops sharply, indicating that insufficient toughening agent is the main factor leading to material embrittlement and the impact performance is significantly deteriorated. The impact strength of comparative example 4 is also relatively low, showing that excessive processing aids cause dispersion defects, making the material easy to break under impact.

[0050] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. An acrylic sheet with temperature-sensitive properties, characterized in that: The invention is prepared from the following raw materials in parts by weight: 60-90 parts of base resin, 5-30 parts of thermochromic material, 0.5-5 parts of light stabilizer, 3-15 parts of toughening agent, and 0.1-2 parts of processing aid; The light stabilizer has a structure shown in Formula 1: Formula 1; Said Z1 is selected from: O, S, N(H), C(CH3)2; The thermochromic material is selected from a metal oxide system in which cobalt oxide and aluminum oxide are compounded in a mass ratio of 1:(3-5).

2. The acrylic sheet with temperature-sensitive properties according to claim 1, characterized in that: The matrix resin is selected from polymethyl methacrylate.

3. The acrylic sheet with temperature-sensitive properties according to claim 1, characterized in that: The light stabilizer is selected from any one of the compounds shown in the following structures: ； ； ； 。 4. The acrylic sheet with temperature-sensitive properties according to claim 1, characterized in that: The toughening agent is selected from: dibutyl phthalate.

5. The acrylic sheet with temperature-sensitive properties according to claim 1, characterized in that: The processing aid is selected from: zinc stearate.

6. A method for preparing an acrylic sheet having temperature-sensitive and heat-sensitive properties according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1 premix: The base resin, thermochromic material, light stabilizer, toughening agent and processing aid are added to a high-speed mixer and mixed for 10-30 minutes to obtain a premix; S2 melt extrusion: The premix was fed into a twin-screw extruder, controlling the temperature of a zone at 160°C-170°C, a zone at 170°C-180°C, a zone at 175°C-185°C, a screw speed of 50-150rpm, and a melt; S3. Compression molding: The melt is pressed into shape by a flat vulcanizer at a pressure of 5-15 MPa for 5-15 minutes, cooled to below 40°C and demolded to obtain a method for preparing an acrylic sheet having temperature-sensitive and thermosensitive properties.

7. The method for preparing an acrylic sheet having temperature-sensitive and heat-sensitive properties according to claim 6, wherein: The die head temperature of the twin-screw extruder in S2 is controlled at 170° C.-180° C., and the vacuum degree is ≥0.08 MPa.

8. The method for preparing an acrylic sheet having temperature-sensitive and heat-sensitive properties according to claim 6, wherein: The cooling in S3 is air cooling.

9. Use of the acrylic sheet with temperature-sensitive properties according to any one of claims 1 to 5 in a temperature indicator, smart packaging or energy-saving windows for buildings.

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